Rat Alk Phos MSCs are isolated from the bone marrow of transgenic Fisher 344 rats that have been engineered to express the human placental alkaline phosphatase gene under the control of the human ROSA26 regulatory element. These cells continue to express hPAP through cell expansion and differentiation. The hPAP can be readily detected by immunocytochemical and histochemical methods as well as in live cells by cell surface labeling and cells can be FACS sorted on the basis of expression.

Highly characterized for surface antigens

To verify that the phenotype of Rat Alk Phos MSCs is in accord with the standard criteria for these cells, four surface antigens were analyzed by flow cytometry. Results. Flow cytometry analysis of cell surface proteins (Figure 1) to characterize Rat Alk Phos MSCs at P3 indicate that these cells express the requisite markers for mesenchymal stem cells: >70% for Positive Markers (CD29, CD73, CD90) and <10% for Negative Markers (CD45).

Unique ability to track cells in transplantation and differentiation studies

There are a wide range of publications that demonstrate using rat MSC for transplantation and differentiation studies. STEMPRO® Rat Alk Phos MSCs Differentiates into all three lineages. Figure 2 shows the induction of Rat Alk Phos MSCs with StemPro® Differentiation Kits (Adipogenic, Chondrogenic and Osteogenic) and it revealed the presence of adipocytes, chondrocytes and osteoblasts/osteocytes by classical differentiation staining.

Easy detection of alkaline phosphatase activity

Expression of the hPAP is stable, allowing the cells to serve as a tracking tool for researchers performing transplantation studies with MSCs. For easy detection of alkaline phosphatase activity, Invitrogen™ offers the ELF® 97 Endogenous Phosphatase Kit. The kit includes the ELF® 97 phosphatase substrate that upon hydrolysis produces a bright and photostable yellow-green fluorescent precipitate at the site of enzymatic activity. This fluorescent precipitate has several unique spectral characteristics, including an extremely large Stokes shift, 180 nm that makes it easily distinguishable from endogenous fluorescence (Figure 3).